The arms of Finland Proper were one of the fields in the arms given to King Gustav I's son John (later to become King John III), when he was given a duchy in Finland [in 1556]. It is probable, that the use of blue flags with yellow crosses had been used even earlier, because in 1569, King John decided that all Swedish flags used at the peace negociations with the Danes in Knäred should be blue with a yellow cross, becasue they had been like that "as of old". However, this is the first official decision known to state this.